The teens ambushed the crowded train at the Coliseum Station in Oakland, stealing from riders and punching several people.
BART officials say two of its police officers were at the station but were patrolling the parking lot.
This comes after other instances of violence at BART:
- Family sues BART after child robbed
- 73-year-old woman attacked on BART
- Registered sex offender accused of San Leandro rape near Bayfair BART
- Report shows spike in phone thefts on BART
- Stabbing victim found at Civic Center BART station
- BART trains delayed at West Oakland by golf club-wielding suspect
- New video shows deadly Oakland BART shooting suspect
Click here for more stories about BART.