NEW YORK, Oct 22: The infamous Washington sniper struck again on Tuesday claiming the 13th victim in almost four weeks of a shooting spree which has left residents in the greater Washington area living is constant fear.

Police launched a massive manhunt after an early morning shooting of a driver on the steps of his idled commuter bus.

Authorities closed major roads and checked vehicles — especially those driven by men — as they scrambled to determine whether the attack in Montgomery County, Maryland, was the work of the gunman who has killed nine people and wounded three since Oct 2.

The latest incident, at around 6:00 am Eastern Time shattered the morning rush-hour routine of the American capital, raising havoc just a day after investigators’ hopes were dashed for a major break in the case that has terrorized the region for nearly three weeks.

“There is no reason for us to believe it’s not from the sniper,” said one of the sources, a high-ranking law enforcement officer.

In a massive effort, helicopters were deployed and an array of law enforcement officials, including FBI, Secret Service and other agents joined the chase. Long lines of traffic snarled the roads. “Witnesses are being interviewed, woods are being combed,” said Montgomery County police spokeswoman Nancy Demme. “They are investigating as if it is related to the other (sniper) shootings.”

Police said the bus driver, who had been waiting at a side street used as a staging area for commuter buses, was shot in the chest as he stood on the top step of his vehicle. He was in critical condition at a local shock trauma center.