Editor's note: This story has been updated with the resolution of the lockdown at Dallas Police Headquarters.
Two days after the shooting that left five Dallas police officers dead and wounded seven more, state and national officials are continuing to offer prayers, calls for unity and praise for the heroism of local law enforcement.
But tensions are still running high in the city. Shortly after 4 p.m., the Dallas Police Department heightened its security after receiving an anonymous threat, a spokeswoman for the department said. WFAA reported that Dallas Police Headquarters was on lockdown, with SWAT being called to a parking garage there to search for a "suspicious person."
About three hours later, Dallas Police tweeted that they had completed a search of the garage and that no one had been found.
Saturday was marked by calls for unity by both Republicans and Democrats. Gov. Greg Abbott's office said in a news release that Abbott spoke with President Barack Obama — a frequent political target for the governor — who offered his condolences for the officers.
But despite moments of conciliation and official calls for healing, the shootings have already become a flashpoint in debates about gun control, policing, and the Black Lives Matter movement.
On Friday evening, Abbott demurred when asked by MSNBC's Brian Williams about Lt. Gov. Dan Patrick's controversial comments earlier in the day blaming the shooting on Black Lives Matter. Instead, he pivoted to emphasize the heroism of Dallas police officers.
And at a Saturday news conference after a NATO summit in Warsaw, Poland, Obama brought up the perpetually fraught issue of gun control, noting that the ubiquity of guns in many American communities contributes to tensions between civilians and police.
"[Police] have a right to come home, and now they have very little margin of error in terms of making decisions," Obama said. "So if you care about the safety of our police officers, then you can’t set aside the gun issue and pretend that that’s irrelevant."
He also noted that many protesters in Dallas were legally carrying firearms, making it more difficult for police to determine the source of the gunfire. Only six states and Washington, D.C., restrict the open carry of long guns such as the one carried by a man whom Dallas police identified as a suspect but later cleared.
Texas Attorney General Ken Paxton later on Saturday disagreed with the notion that stricter gun laws would have stopped Micah Xavier Johnson from carrying out his attack.
"In Texas, we've always believed in the Second Amendment," Paxton said in an interview on MSNBC. "We believe that law-abiding citizens have the right to protect themselves. And in this case, people that are willing to murder people are not going to follow other laws any more than they're going to follow a law that prevents them from killing people."
Abby Livingston and Terri Langford contributed to this report.