Montgomery County Police charged Tyler Tessier, 32, in the murder of his girlfriend, Laura Wallen, who was reported missing on Sept. 4. (Claritza Jimenez/The Washington Post)

From the time Laura Wallen went missing 11 days ago, her family had suspicions about Tyler Tessier, her longtime on-again, off-again boyfriend.

They knew he was the last person seen with the well-liked high school teacher. They believed that a series of text mes­sages sent from Wallen’s phone were actually written by Tessier in an attempt to cover his tracks.

So several days ago, when Montgomery County detectives asked the family about having Tessier, 32, come to a planned news conference on the case — a tactic designed in part to see what he might say in front of TV cameras — the family was more than willing to go along. Even if they knew that it meant sitting next to him and feigning that everyone was pulling together.

“It was all we could do to be seen as a unified family with him,” Wallen’s father, Mark, said Thursday. “And it was absolutely the hardest thing that my wife could do would be to sit next to him and hold his hand. And she had to hold his hand with two hands because she was shaking so badly.”

Laura Wallen and Tyler Tessier (Photos from Montgomery County Police)

On Wednesday, two days after the news conference, police found Wallen’s body — in a shallow grave in the northern part of the county. Hours later, Tessier was under arrest, charged with first-degree murder.

“He is a monster and he is a liar,” Mark Wallen said.

An autopsy shows that Laura Wallen, 31, had been shot in the back of the head, Montgomery police said late Thursday.

Since she was reported missing on Sept. 4, her case has received widespread attention. Wallen was four months pregnant, lived in the D.C. suburb of Olney, Md., and had taught social studies at Wilde Lake High School in Columbia since 2014. She was excited about the school year starting and didn’t seem at all like a person who would take off on her own, family and friends said.

Behind the scenes, detectives were in constant contact with Tessier, a landscaper believed to be the father of Wallen’s unborn child. They said he couldn’t keep his story straight, was slow to reveal he had recently become engaged to another woman, and was making unexplained trips to a wooded area in the northern part of the county.

A police search team, with ­cadaver-sniffing dogs, scoured the area Wednesday. They found recent tire tracks, followed them and came across a freshly dug area, according to police. That’s where they found Wallen’s body, they said.

In court Thursday — Tessier’s first appearance in the case — an attorney representing him, Victoria Kawecki, did not comment on the police allegations. But she noted that Tessier had no criminal record and had an extended family who supported him. She asked the judge to set a bond that would allow him to be released from custody pending further court proceedings.

Montgomery County Chief of Police J. Thomas Manger spoke about the arrest of a suspect in the case of a missing pregnant woman found dead on Sept. 13. (WUSA9)

Prosecutor Donna Fenton laid out the state’s case against Tessier, saying he had admitted sending the fake text messages from Wallen’s phone, tried to hide Wallen’s car and gave detectives “hundreds of inconsistencies.”

District Judge Zuberi B. Williams ordered Tessier held without bond. “I do think that you are a danger to the community,” Williams said.

In court papers, detectives said Wallen and Tessier’s new fiancee “both believed he was dating them exclusively.” The detectives said that may point to a motive for Tessier to kill Wallen.

The two women apparently were in contact recently, the court papers show.

On Aug. 28, about a week before Wallen disappeared, she sent a text to the fiancee, stating: “It’s important that some things are cleared up and I would imagine that if you were in my position, you’d want some answers as well. By no means is this an attempt at confrontation, just looking for an explanation . . . woman to woman.”

At Tessier’s bond hearing, Wallen’s family sat in the front row. Afterward, they talked about their support for the detectives’ efforts, including the news conference that helped draw more attention to the case.

“We were pretty sure it was Tyler, but we didn’t know where she was,” Mark Wallen said of his daughter.

He said detectives worked the case “with supreme precision and during this whole process kept us as updated as they possibly could. . . . We were praying for a good, old-fashioned miracle. God did not give us the miracle that I asked for, but he did give us a miracle nonetheless. We have our daughter back.”

On Wednesday night, Montgomery Police Chief Tom Manger said investigators made “a calculated decision” to allow Tessier to attend the news conference.

When Tessier spoke, he pleaded for Wallen to contact her family and asked for her safe return, saying: “Laura, if you’re listening, it doesn’t matter what’s happened. It doesn’t matter what type of trouble. There’s nothing we can’t fix together.”

In Olney, a neighbor of Laura Wallen’s, Beth Clay, said in the days after Wallen’s disappearance that boxes from Old Navy and Bed Bath & Beyond began piling up at Wallen’s door. Clay, 56, who has lived beside Wallen for five years, took them inside for safekeeping and alerted Wallen’s family, all the while thinking that “this is not a girl that was going to hurt herself.”

The two had talked regularly, and over the summer Wallen often would be on her second-floor patio making jewelry, sometimes scurrying down to Clay’s patio below to retrieve a bead she had dropped.

Throughout Alicia Waxman’s five-year friendship with Wallen, they would discuss her relationship with Tessier, Waxman said Thursday. Her eldest son is a former student of Wallen’s.

Waxman said the couple had been “off and on” for about 10 years, and Wallen had talked about his reluctance to propose or make a commitment to her. In Waxman’s mind. the pair were a “strange, mismatched couple,” with Tessier “very cold” and Wallen an “angel who literally spread light and love.”

At Wilde Lake High on Thursday, Wallen was recalled as gregarious, encouraging and supportive.

One student recalled how she would open wide her arms, wiggling them as a greeting.

“Come here, give me the jellyfish hug,” Wallen would tell her students in Howard County, according to a former student, Aiyanah Moore.

The almost daily hugs had students referring to her as “Wallaby with the jellyfish hugs,” said Moore, 18, who took Wallen’s world history class as a senior last year.

Moore said Wallen paid equal attention to students who needed more help and those who, like her, quietly did their work. Wallen encouraged Moore to pursue her goal of becoming a Navy pilot, even when the student doubted she could do it.

“She just had the personality that kind of draws your attention,” Moore said. “Ms. Wallen, she actually cares about her students.”

Another former student, Hamad Wasti, remembered his first day of class as a junior at Wilde Lake in 2015. When Wallen conducted attendance, Wasti jokingly told her he wanted to be called “OG” — shorthand for “original gangster.”

Wasti, now at Howard County Community College, said Wallen used the nickname the rest of the school year.

“She called me OG every day and only referred to me as OG to make me happy,” Wasti wrote in a message on Twitter. “It would put a smile on my face every time. She was such an amazing lady. She did whatever she could to make us happy.”

Tessier worked for Ruppert Landscape for about 2½ years, leaving the company in 2011, said Amy Snyder, a spokeswoman for Ruppert, a business that has been in Montgomery County for about 45 years.

She declined to say more about Tessier.

“We’re just sorry this happened,” Snyder said. “Our hearts go out to the Wallen family and everyone in the community who has been affected by this.”

On Sept. 7, police found Wallen’s car unoccupied and parked in an apartment complex in the 10600 block of Gramercy Place in Columbia, a five-minute drive from the school. Police said Tessier brought the car there after removing the front license plate .

Police said they believe Wallen was killed Sept. 3, a day after a surveillance video at a grocery store showed her and Tessier together.

Wallen’s sister received several texts from Wallen’s phone on Sept. 4, stating that the child she was carrying probably was not Tessier’s but might be that of a previous boyfriend, Manger said.

The chief said police determined those texts had been sent by Tessier.