Elmer Campos Hernandez appeals for information to find his brother’s killers at Montgomery County Police Headquarters in Gaithersburg. (Michael Laris/The Washington Post)

Elmer Campos Hernandez was in bed early Sunday when he was jarred awake by a commotion outside his Aspen Hill home.

Overnight disturbances are common in his neighborhood, he said, and he usually goes to the window to see what’s happening. This time, he tried to ignore it.

Outside, his brother, Edwin, 28, was being held up by two men, who ended up shooting him multiple times. He died later at a hospital.

“I heard it, and I didn’t pay any attention,” Campos Hernandez said Tuesday. “Maybe if I did . . . I’d have an opportunity to stop this.”

Campos Hernandez teared up as he stood in a basement conference room at Montgomery County’s police headquarters in Gaithersburg, the police chief on his left and a translator on his right. The immigrant from El Salvador appealed for help in finding his only brother’s killers.

“He was just like my right hand,” Campos Hernandez said. “My soul hurts because now I have to get used to living without him.”

Police said the type of attack that killed Elmer’s brother — an attempted robbery turned homicide among apparent strangers — is uncommon in the county. It punctuated an unusually violent two-week stretch in Montgomery, with authorities also investigating a pair of home-invasion killings, a hit-and-run being probed as a homicide and a shooting that left a man dead on a paved path.

In another development, a 21-year-old man was found gravely wounded about 4:30 p.m. Tuesday in a park about half a mile south of the site of Sunday’s fatal shooting. Police said it was far too early to link the incidents.

Police Capt. Paul Starks said that in the four other incidents, there appeared to be some connection between the killers and the victims. A law enforcement official said some of the cases may have been drug-related. Although Starks would not confirm that, he sought to reassure residents worried that the victims “could have been me.”

“We’re saying, ‘No, it couldn’t have been, unless you had a known relationship’ ” with the killers in those crimes, he said.

Authorities have provided only limited information about the incidents, citing the investigations and the need to protect would-be witnesses.

On Dec. 3, Cesar Smith, 45, of Gaithersburg died of a stab wound after a group of men entered the apartment he was in on Whetstone Drive in Gaithersburg.

On Dec. 5, a 34-year-old man died in a hit-and-run after he and his brother got a ride in a black Honda. The Honda’s driver struck the brothers on West Diamond Avenue in Gaithersburg, according to the surviving brother, who was also 34 at the time of the accident.

On Dec. 7, Jesse Patrick Campos, 21, was fatally shot in his apartment in White Oak after two people forced his roommate to open the door. Jesse Campos is not related to Edwin Campos Hernandez.

On Dec. 10, Christopher Davon White, 22, of Landover was shot multiple times near Castle Boulevard in the Briggs Chaney area.

The events appear to be unconnected, police said.

Edwin Campos Hernandez’s shooting was distinct, Starks said. “What makes this different is this is a random event,” he said.

Campos Hernandez had taken a cab home from a birthday party, his brother said. After he got out of the taxi outside his apartment complex, two men approached along the 3700 block of Bel Pre Road, Lt. Greg Wise said.

“It was an announced robbery from the start,” Wise said.

Police said they don’t think the robbers came away with anything because Campos Hernandez didn’t have much.

Elmer Campos Hernandez said his brother was peaceful. “He never had any issues with anybody,” he said. He called for more security in the area and asked any witnesses to speak up.

“Today was my brother,” Campos Hernandez said. “Tomorrow might be someone else.”