BART cops, apparently tired of shooting at unarmed men and tasing children, are now shooting each other.

Investigators are trying to figure out how 42-year-old BART sergeant Tom Smith, a 20 year veteran of the force, was fatally shot by a fellow officer as they searched a suspect's Alameda County apartment.

The officers were at an apartment complex serving a warrant regarding "some crimes that had occurred on a train." The suspect, who was already in custody, was wanted in connection with specific robberies, according to California governor Jerry Brown.

The officers, clad in bulletproof vests, knocked on the suspect's door but heard no response. Because the door was unlocked and the suspect was on probation (so no warrant was necessary) they entered the suspect's one bedroom apartment. Smith never exited.

"During that search, it appears one officer accidentally fired his weapon, which struck the other officer and ultimately it was a fatal shot," said Nelson, the Sheriff's Department spokesman.

The firing officer, who was not named, has been on the squad for more than a decade.

[image via AP]