Biker in stab spree: cops

A skateboarder and another man were fighting for their lives after being attacked by a bicyclist, who sources said was on a multiborough stabbing spree across the Williamsburg Bridge Saturday.

The first victim, a 30year-old man on a skateboard, got into a dispute with Omar Cartagena, 44, who pulled a knife and stabbed him once in the chest on the bridge’s bike path at about 10:30 a.m., police and sources said.

The victim was taken to Elmhurst Hospital in critical condition, according to the sources.

Shortly after 1 p.m., a 34-year-old man was stabbed in Sarah D. Roosevelt Park on the Lower

East Side, 10 blocks from the Manhattan entrance to the bridge, sources said. The victim was taken to Bellevue Hospital in critical condition, according to the NYPD.

An NYPD spokesperson didn’t confirm Cartagena’s involvement in the second stabbing but said a possible connection was under investigation.

Sources said Cartagena is suspected of fleeing the Manhattan scene on his bike, riding across Delancey Street and back over the bridge into Brooklyn.

Cops arrested him around 2:30 p.m. at Havemeyer Street and Borinquen Place, where cyclists enter the bridge in Williamsburg, police said.

The incidents remain under investigation, cops told The Post.