A 21-year-old man was clinging to life Thursday after he was shot in the head on a Bronx street corner, police said.

The shooting happened just three hours before Police Commissioner Jessica Tisch proudly announced that the NYPD has taken 1,000 guns off the street so far this year.

The victim was on the corner of Jerome and Bainbridge Aves. in Norwood around 9:45 a.m. when the gunman stormed up to him and opened fire, witnesses told police.

EMS rushed the victim, suffering from a head wound, to St. Barnabas Hospital, where he remained in critical condition.

The gunman ran off, cops said.

Responding officers took someone into custody at the scene, a police source with knowledge of the case said. He was being questioned by detectives Thursday afternoon.

No charges were immediately filed.

As of Sunday, cops had investigated 121 shootings in the city, one fewer than this time last year.

After a record-breaking cold snap in January that contributed to a drop in crime, shootings jumped by 20% in the last four weeks compared to the same period last year, from 39 to 47, according to NYPD statistics.