[UPDATE BELOW] The NYPD has directed uniformed members of service to be assigned to work in pairs, not solo, in the wake of last night's sniper attack in Dallas, where five police officers were killed and seven wounded during an ambush at a protest against police shootings. An NYPD source says the directive is in effect until further notice.

Police were last ordered not to work alone after the December 2014 execution-style slaying of two NYPD officers as they sat in their squad car in Bed-Stuy. Today's directive is not in response to any reported credible threat, but merely a precaution against potential copycat attacks.

Mayor de Blasio announced this morning that he will attend a closed-door NYPD senior leadership meeting at One Police Plaza to discuss the events in Dallas. It's unclear if NYPD Commissioner Bratton is planning a press conference today to discuss the incident; we'll update as more information becomes available.

UPDATE: Security is being beefed up at every precinct stationhouse, and ABC 7 obtained a copy of today's department-wide memo, part of which reads, "All members of the service are reminded to think tactically and remain vigilant at all times while in uniform and should remain alert especially when members of the public approach them. Members are to always be aware of any suspicious behavior and to be alert of their surroundings, whether on or off duty."

In an interview this morning, de Blasio promised that there will be "a very, very strong police presence" at any political protests planned for today.