Among police officers, it’s known as the “sixth sense” — the acquired, almost supernatural, ability of policemen to predict and anticipate danger before it occurs.

Senate Sergeant-at-Arms Terrance Gainer said the eerie, nagging gut instinct shows officers have a “nose for the street.”

Unfortunately for Capitol Police Officer Eddie Thornton Jr., he was off duty, out of uniform and without backup or a bulletproof vest when his sixth sense kicked in during the summer of 2009.

It was his birthday, his day off and, he thought, a good time to visit his mother. But as he pulled his pickup truck into the children’s day care center in Prince George’s County that his mom owned and operated, a nearby resident ran toward Thornton and his mom saying he heard gunfire.

The frightened man had phoned the police, but no one had arrived at the scene when 24-year-old Badara Samb ran into the parking lot at 8500 Greenbelt Road with a gun.

Thornton knew something was wrong: The young man didn’t look like a police officer, but he was wearing a police-duty belt, carrying an officer’s gun and had a frantic look on his face.

Seconds later, Samb opened fire, shooting randomly at cars and in the air.

Thornton brandished his gun, which he always carries, told his mom to hide in her car and returned fire.

“I just knew I needed to stop him before he hit someone,” Thornton said in an interview.

Samb, a schizophrenic who had stopped taking his medication and stolen the gun from his roommate, a military police officer, stopped shooting when Prince George’s County police officers arrived.

Area residents and passersby later claimed to have heard 15 to 20 gunshots during the 15-second exchange of fire.

It wasn’t until a few minutes later, after the adrenaline rush subsided, that Thornton felt a prick of pain.

“I didn’t realize that I was hit until someone told me,” he explained.

A bullet had entered his lower back on the left side and exited on his right. Thornton was rushed to the hospital along with a 12-year-old girl who’d been hit in the crossfire.

More than a year later, the case and investigation were finally closed. The gunman was not found criminally liable for two counts of attempted murder because of his mental condition, but he was deported to his native country, Senegal.

Capitol Police Chief Phillip Morse nominated Thornton for the National Law Enforcement Officers Memorial Fund’s Officer of the Month — a nationwide recognition that no Capitol Police officer had ever received.

And this month, the memorial fund named Thornton Officer of the Month for December.

“It’s a great honor among police officers,” said Thornton, 32, who has been an officer for seven years. “It’s not given to many.”

But Thornton, who also received the 2010 Officer of the Year Award from the Capitol Hill Executive Service Club and the USCP Medal of Valor, refuses to stand on a pedestal for “just doing my job.”

“I’m not a person that likes to be out in the public eye,” said Thornton, who returned to his position in the USCP House Division 44 days after the shooting, as soon as the doctors affirmed his full recovery. “I did what I was supposed to, and I’m glad everything turned out OK. I take it as an honor for the people at Capitol Police who taught me everything I needed to know and were there for me in the [recovery] process.”

Thornton is not the only officer with that mentality.

“When you’re out there, you’re in uniform,” Morse told Roll Call in an interview in October. “People in need don’t care what rank you are or what police department you’re from. They just need help, and of course that’s what we do and why we chose this profession.”