Here's what you need to know about Mohammad Youssef Abdulazeez, the gunman who opened fire at two military facilities in Tenn., killing four Marines. (Alice Li/The Washington Post)

The gunman who targeted U.S. military service members in a late-morning shooting Thursday in Tennessee was a 24-year-old electrical engineer who had grown up in Chattanooga as part of a conservative Muslim family.

Mohammad Youssef Abdulazeez was born in Kuwait but moved with his family to the United States as an infant after the start of the Persian Gulf War and became a U.S. citizen, according to accounts given by friends and one of his sisters.

He attended Red Bank High School, just outside Chattanooga, north of the Tennessee River. His senior yearbook entry featured two photographs of him — cleanshaven with close-cropped hair — alongside a prophetic quotation: “My name causes national security alerts. What does yours do?”

In high school, Abdulazeez was active as a wrestler, competing in the 189-pound weight class. He later competed briefly on the mixed-martial-arts circuit, training at the Chattanooga Fight Factory, a local gym.

A video of one cage fight from 2009 shows him pummeling a middleweight from Shelbyville, Tenn., winning in the second round on a technical knockout. Accounts of the bout were posted at the time on several Web sites.

After graduating from high school, Abdulazeez remained in the area, earning his engineering degree from the University of Tennessee at Chattanooga in 2012.

His family was rooted in the community of Hixson, a Chattanooga suburb. His father, Youssef, was employed by Chattanooga’s Public Works Department. A senior U.S. law enforcement official confirmed that Abdulazeez’s father was investigated by the FBI several years ago and put on the terrorism watch list but was later removed.

A sister, Dalia, taught fourth grade at Woodmore Elementary School. In 2009, the staff and student body surprised her with a schoolwide assembly to celebrate her naturalization as a U.S. citizen, singing, “My Country, ’Tis of Thee.”

Visa Harper, a former principal at Woodmore High School, recalled Dalia Abdulazeez as a competent and sweet young woman who wore Muslim headscarves and loose-fitting, modest clothing. She so impressed her sponsor teachers during her student teaching year that Harper hired her to teach fourth grade.

A few years later, however, the young teacher surprised Harper by saying she would have to resign for personal reasons.

“When she was about to leave, she mentioned a dilemma with the guy she wanted to marry. Her parents didn’t approve,” Harper said. “She was leaving the country and going with him. She didn’t care what her parents said.”

“I got the sense [her parents] were very religious,” Harper added. “I got the sense they wanted to pick who she would marry.”

Another sister, Yasmeen, drew attention at Red Bank High School and the University of Tennessee at Chattanooga for proudly wearing a traditional Muslim headscarf in class and on the volleyball court.

Yasmeen told the Chattanooga Free Press in 2010 that some students harassed her but that she wasn’t afraid to confront people about their attitudes toward her religious beliefs. “I’m not afraid to go straight toward them and ask them, ‘Do you really know what Islam is?’ ” she said. “There’s this misconception that Islam is a violent religion. Muslims are actually peaceful.”

The shooting also resonated inside a massive apartment complex in Falls Church, Va., where relatives of Abdulazeez live among immigrants from Africa, the Middle East and Latin America. Abdulazeez had recently visited his family here, and his cousin said he noticed nothing wrong or amiss with Mohammad.

“I’m shocked, I’m just shocked,” said Abraham Abdelaziz , who said he is Abdulazeez’s cousin and stood at his door with tears welling in his eyes. “I don’t know what else to say. I just heard about it. I’m totally shocked.”

According to a résumé he posted online, Abdulazeez held engineering internships with the Tennessee Valley Authority and at least two private firms.

A few months before Thursday’s shootings, he had a scrape with the law. In April, he was charged with driving under the influence in Chattanooga, according to court records. A booking photo from the arrest shows him with a half-smile and a full beard. He was to appear in court July 30.

Abdul Baasit, the imam at the Islamic Society of Greater Chattanooga, said he saw Abdulazeez recently at the mosque during Ramadan. “I am still trying to gather myself,” he said.

Adam Goldman, Alice Crites, Julie Tate, Jennifer Jenkins and Antonio Olivo contributed to this report.