SAN FRANCISCO — A San Francisco police officer who killed himself after being pulled over by police in a neighboring city was under investigation for child sexual abuse in Las Vegas, authorities said Tuesday.

Antonio Cacatian, 49, shot himself Monday afternoon after San Francisco police requested help arresting him. Police in the nearby city of Richmond, where Cacatian lived, pulled him over in a shopping mall parking lot and officers retreated to their cars when they heard a gunshot, Lt. Felix Tan said.

Tan said the windows of Cacatian’s vehicle were tinted and officers could not see inside.

A San...