A fourth suspect, a 20-year-old Santa Barbara man, has been arrested in connection with last week’s slashing death of Robert Burke Simpson at Arroyo Burro Beach.

Detectives detained Adrian Robles on Tuesday night at a home in Ventura, Santa Barbara County Sheriff’s Department spokesman Drew Sugars said in a news release late Wednesday afternoon. Detectives were assisted by the Ventura County Sheriff’s Department and Santa Barbara police.

Robles, facing homicide charges, was being held in the Santa Barbara County Jail without bail.

Rudy Gallegos, 21, of Santa Barbara, was arrested on suspicion of homicide on Sunday as detectives served a search warrant at his residence. He is being held in the county jail without bail.

Brittany Danielle Weiler, 19, of Santa Barbara, was arrested Friday and a 17-year-old girl was arrested the next day, both as alleged accessories to murder.

Weiler is in the county jail on $1 million bail and is scheduled to be arraigned Thursday. The juvenile is at Juvenile Hall.

Sugars said detectives have arrested all four suspects believed to be present during the fatal attack on 44-year-old Simpson, but that they are continuing the search for others who may be accessories to the crime.

Anyone with information related to the slaying or its aftermath is asked to call detectives at 805.681.4150. Witnesses coming forward have already been helpful in piecing together the evening’s events, and Sugars urges people to call in even if they’re not sure their information has any bearing. Witnesses wishing to remain anonymous can leave a message on the the sheriff’s Anonymous Tip Line at 805.681.4171.

Simpson was stabbed about 6:30 p.m. last Thursday during an altercation near the grassy picnic area at the popular beach, 2981 Cliff Drive. Witnesses say the Mesa resident was attempting to break up a fight when a young man ran up behind him and slit his throat.

Authorities estimated that several hundred people were in the park at the time of the confrontation, with the Boathouse Restaurant packed with patrons and the Surfrider Foundation’s Santa Barbara chapter holding an event nearby.

Several people rushed to Simpson’s aid but he died of his wounds.

Noozhawk managing editor Michelle Nelson can be reached at mnelson@noozhawk.com. Noozhawk publisher Bill Macfadyen contributed to this report. He can be reached at wmacfadyen@noozhawk.com.