Washington ( CNN ) -- An officer with Washington 's Metropolitan Police Department came under an unprovoked attack Friday from a man wielding an ax , police said , the second such attack in two weeks that is prompting warnings and new protocols to officers on the job . The attack , and another last week in which a man attacked four New York City officers with a hatchet in Queens , prompted an immediate increase in security for officers in both D.C. and New York . The New York Police Department said in a memo : `` Police Officers on patrol should maintain a heightened level of awareness . '' The attack in Washington occurred around 3 a.m. as the officer was sitting in his marked squad car in Washington 's Brookland neighborhood , near the campus of Catholic University of America , police said . The officer , who has n't been identified , was n't injured by the ax , but he chased the suspect and suffered a shoulder injury in a scuffle before the attacker ran away , police said . No motive is known and the suspect remains at large . Police said he was an African-American man about 6 feet tall and of stocky build . A photo provided to CNN by a law enforcement official shows the ax implanted in the window of the police car , just inches away from where the officer 's head was inside the car . Metropolitan Police Chief Cathy Lanier issued a warning to officers to increase their vigilance for their safety , amid concern about recent attacks on authorities in New York and Canada , a law enforcement official told CNN . In reaction to the Washington attack , the NYPD issued new patrol protocols to its officers to increase security , including `` Effective immediately , all foot posts are to be assigned in pairs of two . There are to be no solo foot posts assigned citywide . '' The memo said officers will be required to remain together and take meal breaks in pairs . Mary Kay Mallonee and Evan Perez contributed to this report .
A D.C. police officer was attacked in his car with an ax Friday , police say . The officer was injured in the shoulder after a scuffle and the attacker got away . Police are looking for two men who they believe were involved in the attack on Officer Michael J. Smith Jr. of the Metropolitan Police.