The Los Angeles County Sheriff's Department said the suspect, only identified as a San Gabriel man in his 40s, had entered the sheriff's station in the 8800 block of Las Tunas Drive to register as a sex offender before he later opened fire in the parking lot at about 7:15 a.m.
While the man was inside the lobby, deputies realized he also had a $40,000 felony warrant against him for a sex crime in Los Angeles.
A deputy asked the man to wait as he sought backup to arrest the man. But when they returned, the suspect ran out of the station. It was unclear if the man was armed when he was inside the station.
Authorities said there was an exchange of gunfire between the suspect and deputies.
The LASD Special Enforcement Bureau Special Weapons Team responded with armored vehicles and officers in tactical gear.
Officers were seen surrounding a dark SUV at the station's parking lot and a flashbang was deployed.
Authorities later confirmed the suspect inside the SUV was dead. According to officials, the suspect appeared to have died from a self-inflicted gunshot wound.
Officials said no deputies were injured during the gunfire.
"This is another assault on deputies and we see these all too frequently now," Sheriff Jim McDonnell said. "Certainly a cause for concern for everyone in our communities."
"Our officers are out there putting themselves between harm and the public that we serve," McDonnell continued. "We're very, very fortunate and we're very, very thankful that no deputies were injured or killed this morning because this could've been a very different day."
A shotgun was recovered from the suspect's vehicle and deputies said they believed there was also a handgun inside as well.
The suspect's identity would not be released pending notification of next of kin.
Las Tunas Drive was closed between Rosemead Boulevard and Muscatel Avenue as the investigation continued.
Anyone with information was encouraged to contact the LASD's Homicide Bureau at (323) 890-5500. If you prefer to provide information anonymously, you may call "Crime Stoppers" by dialing (800) 222-TIPS.