If you are going to judge cops in general by videos, include one that shows Cpl. Bryon Dickson and Trooper Alex Douglass being gunned down by a sniper outside the Pennsylvania State Police barracks in Blooming Grove on Friday night.

Make sure you consider the bravery of the fellow troopers who risked becoming victims themselves while hurrying to assist the dying Dickson and the critically wounded Douglass.

Imagine their heartbreak when they were unable to save Dickson, the fourth cop in nine days in to be shot to death in a nation that paid scant attention other than in the particular community suffering a loss.

And keep in mind the hundreds of cops who were combing the northeastern Pennsylvania woods on Tuesday for a highly skilled marksman who allegedly perpetrated the unprovoked ambush out of an avowed hatred for the police.

At any instant, 31-year-old Eric Frein could have been raising his rifle and putting another cop in the crosshairs of his telescopic sight. The suspect’s father, Michael Frein, told the police who came to search the family home in Canadensis, Pennsylvania, that he had taught his son to shoot as a boy. The son had been on the rifle team at Pocono Mountain High School and had become a better shot than his father.

“Doesn’t miss,” the elder Frein said of his son.

The father was a retired Army major with 28 years of service, and the son had become involved in military reenactments, apparently working at one point as an “armorer’s assistant” for a company that produced them. Eric Frein’s one prior serious brush with the law had come after he was accused of burglary and grand larceny from a World War II reenactment in Catherine, New York. He had made arrangements to surrender but failed to show and was picked up as a fugitive in Pennsylvania. He was held on $75,000 bail, but the case was resolved without him receiving a significant prison sentence. There seems to be nothing in his life to explain the anti-cop vitriol he is said to have spewed in social media and to people who knew him.

“He has made statements about wanting to kill law enforcement officers and also to commit mass acts of murder,” state police Commissioner Frank Noonan told reporters on Tuesday. “What his reasons are, we don’t know. But he has very strong feelings about law enforcement and seems to be very angry with a lot of things that go on in our society.”

Frein hardly kept his views secret, which raises the question of why nobody sounded an alarm.

“As we’ve interviewed a number of people, that’s been the common theme: This was not a surprise,” state police Lt. Col. George Bivens said.

Frein had become a self-declared survivalist, but when he was not off in the woods he was living at least on and off at his childhood home, driving a green Jeep registered to his parents, taking exercise strolls with his mom, Debbie Frein. He did not even have his own guns, though his family owned two, an AK-47 and a .308 rifle outfitted with a telescopic sight. One thing he could still do well was fire a bullet exactly where he wanted it to go.

Eric Frein apparently remained close to his older brother, Michael Frein, serving as best man at his wedding in 2006. The Standard Speaker reports that Michael Frein lives in the same housing development as Trooper Douglass, which gives investigators cause to wonder whether the attack on the barracks was as random as it might have seemed.

On the surveillance video from the Blooming Grove barracks, Dickson can be seen emerging in full uniform from the front door minutes before the end of a 3 p.m.-to-11 p.m. tour. The 38-year-old Marine veteran is seconds from climbing into his car and returning to his wife and two young sons when he suddenly goes down with two fatal bullet wounds.

“He immediately dropped to the ground in front of the door where he remained motionless,” the criminal complaint says.

Police communications officer Nicole Palmer had arrived to start work moments before, passing Dickson in the lobby as he exited and she entered. She now heard a sound that made her think of firecrackers. She gazed outside to see Dickson sprawled on the ground. She hurried out and asked him what had happened.

“He said he had been shot and needed help,” the complaint says.

As Palmer did what she could to assist Dickson, another shot rang out. Palmer saw a cloud of white dust kick up. She retreated into the lobby, but only to call for backup and an ambulance. She could have just sought safety inside, but she returned to Dickson.

“He asked her to bring him inside,” the complaint says.

She did her best to move him.

“But she was unable to.”

In the meantime, Douglass had pulled into a lower parking lot to start an 11 p.m.-to-7 a.m. shift. He saw Dickson as he came around the front of the building and was starting toward him when a fourth shot rang out.

“At which time he fell to the ground,” the complaint says. He had been hit.

Douglass managed to crawl inside. The video surveillance would show that 90 seconds had passed between the first shot and the fourth and final one.

Other troopers used a police car as a shield as they carried Dickson inside. He was pronounced dead at the scene. Douglass was Medevaced to a hospital in Scranton, where he was stabilized.

Back at the barracks, police conducted a shoulder-to-shoulder “line search.” Trooper George Murphy found four spent .308 shell casings.

“The casings were located in an area consistent with the area where the shooter would have positioned himself to shoot Cpl. Dickson and Tpr. Douglass,” the complaint says.

The police soon picked up a “person of interest” who had been a cop himself until he was fired for beating his girlfriend. He ceased to be of interest on the morning of September 15, after a man named James Novak called police. Novak reported that he had been walking his dog in the woods when he came upon a green Jeep mired in the muck of a small retention pond.

“He was suspicious because it was abandoned with its windows opened,” the complaint says.

Trooper Jeremy Carroll responded. He saw a chain barrier covered with PVC piping that the Jeep had apparently struck and damaged before becoming stuck. Carroll noted that the vehicle had a Pennsylvania plate, DJV5220, registered to Michael and Deborah Frein. It had not been reported stolen.

The vehicle was towed to Ray’s Auto Repair in Milford. The troopers obtained a search warrant and discovered two spent .308 shell casings under the rear passenger-side seat that matched the casings recovered from the murder scene. They also found a valid driver’s license, a Social Security card, and a Pennsylvania Game Commission Range Permit, all in the name of Eric Frein. The license gave his height as 6-foot-1 and his weight as 165 pounds, and noted he has blue eyes.

Other recovered items were camouflage face paint, a black hooded sweatshirt, flashlights, two empty rifle cases, and what the complaint describes only as “various information concerning foreign embassies.”

The following day, September 16, police secured a search warrant for the address on the driver’s license, the Frein family home. The father told police that he was a retired Army major, having served 28 years. He also said two weapons were missing from the home, the AK-47 and the .308 rifle. Cops found 14 spent .308 shell casings in the garage and a book called Sniper Training and Employment in the son’s bedroom.

“The art of sniping requires learning and repetitiously practicing those skills until mastered,” says the introduction to this manual published by the Pentagon. “Perfection must be reached.”

The police had reason to give thanks that Eric Frein had not perfected the art of getting away, if the stuck Jeep was any indication. He otherwise might have made it home undetected. The best guess now was that he was still in the woods with those two rifles.

And this meant every officer who went in there was facing the direst danger while his family was at home, worrying that their loved one might be the next to fall victim to a this cop-hating gunman.

The funeral for Dickson is scheduled for Thursday morning at St. Peter’s Roman Catholic cathedral in Scranton. His murder has been followed by the killing of a deputy down in Georgia, bringing the nationwide toll since his death to five cops shot to death in the space of 11 days.

Everybody’s hope as of Tuesday night was that Frein would be caught without another cop having to make a sacrifice from which his family would never recover.

And the rest of us so quickly forget.