How the suspect was identified in the killings of 4 men in Los Angeles County

A suspect has been arrested in connection with the killings of four men in four days in Los Angeles County, police announced Saturday.

Three of the victims were sleeping homeless men who were killed in three different locations throughout the city.

The fourth was a Los Angeles County employee, whom the attacker followed home and then robbed before he shot and killed him.

Police arrested Jerrid Joseph Powell, 33, in connection with the follow-home robbery killing before they connected him to the three other killings.

Here's a timeline of how the four killings unfolded.

Sunday, Nov. 26

At about 3 a.m., a 37-year-old Hispanic man, Jose Bolanos, was fatally shot while he was asleep on a couch in a rear alley near 110th Street.

Police Chief Michel Moore said at a news conference Saturday that the man was killed "brutally and ruthlessly."

Monday, Nov. 27

The second killing occurred around 4:55 a.m. on East 7th Street. Mark Diggs, 62, was shot near a rear wall. Moore said he had been pushing a shopping cart and had leaned himself against a wall when someone approached and shot him.

"It was chilling," Moore said Saturday, recounting video of the crime. "The coldblooded manner in which he walks up and shoots this individual without any hesitation, no interactions, and then leave that location and — and we now know — to follow home an individual, a young father of two, who's simply charging his car."

Tuesday, Nov. 28

Nicholas Simbolon, 42, was found dead in his garage in the city of San Dimas, near Los Angeles, by a relative at 6:48 p.m.

Los Angeles County Sheriff Robert Luna said Thursday that it appeared Powell had followed Simbolon home from an electric vehicle charging station 12 miles from his house.

After Simbolon pulled into his garage, police said, the attacker robbed Simbolon of "some personal belongings" before shooting him and fleeing.

Wednesday, Nov. 29

Less than 24 hours later, at 2:30 a.m., a 52-year-old man who had been sleeping on the sidewalk was fatally shot near an intersection, police said.

Thursday, Nov. 30

Police arrested Powell early Thursday in Beverly Hills on charges of murder and robbery.

Beverly Hills police detectives were able to identify his car and match the license plate to the vehicle used in the killing Tuesday, leading to a traffic stop arrest.

Moore said Saturday that authorities were then able to match the vehicle and its license plate to the car they identified as having been driven by the person believed to be responsible for the three killings of homeless men, connecting Powell to those crimes, as well.

A handgun found in the car Thursday matched the weapon used in the killings of the three homeless men.

Friday, Dec. 1

Police announced at a news conference that they were searching for a gunman in the shootings of the homeless men.

Moore said police formed a task force to search for and identify a suspect, pulling homicide detectives from all over the city.

Mayor Karen Bass said the city would open emergency shelters to house homeless people.

“Our message to the unhoused community is clear: Do not sleep alone tonight,” Bass said at the news conference Friday. “Seek shelter, seek services, stay together.”

Saturday, Dec. 2

Moore laid out at a news conference how investigators connected the dots between the shootings.

Homicide detectives investigating the shootings Monday and Wednesday discovered that the shell casings in the two cases were similar and that there had been a similar case last Sunday in another bureau.

The task force that was assembled identified the vehicle that was seen at all three Los Angeles shootings — a 2024 BMW M440 — and started to try to find it, Moore said.

They learned it was in the custody of the Los Angeles County Sheriff's Office in connection with the San Dimas homicide. They then worked to determine whether the weapon found in the car was the same one tied ballistically to the three Los Angeles shootings, Moore said.

He said they worked overnight into Saturday morning to connect the weapon to all four homicides.

This article was originally published on NBCNews.com