An off-duty NYPD officer has been hospitalized in critical condition after he was attacked in the Bronx early Tuesday morning.

The 48-year-old officer, who has not been identified, was jogging at around 10:30 a.m. when at least three men jumped out of a black Honda sedan and then repeatedly struck the officer in the head and stole his cellphone, car keys and wallet, police said.

The officer was taken to Jacobi Hospital, where he is currently in critical but stable condition, Fox 5 reports. Police say the officer sustained a fractured skull and brain bleeding as a result of the attack. 

The NYPD said detectives believe this attack is linked to a series of robberies this summer in the city. Police said the same crew of thieves could be responsible for at least 19 robberies.