An armed man was holding dozens of people hostage on a public bus Tuesday in Rio de Janeiro and threatening to set the vehicle on fire, Brazilian police said.

Axar.az reports citing Time that the Federal Highway Police said negotiations were underway with the man who has been holding 37 people hostage since about 5:30 a.m. on a busy bridge linking the suburb of Sao Gonçalo to downtown Rio de Janeiro. At least six hostages have been released so far and police said they told authorities the man had spilled gasoline in the bus and threatened to set it on fire. Officials said the man has identified himself as a policeman but this has not been confirmed.

The man has not made any particular demands and appears to have “psychological problems,” a spokesperson for the traffic police said.

The man who earlier today hijacked a bus in Brazil was shot by a police sniper, according to a live feed by Globo. The hijacker was apparently killed, although there has been no confirmation of this information.