Richard Dennis was startled when he heard someone banging on his backdoor around 11:30 p.m. Tuesday, authorities say. The 61-year-old gripped a gun as he stepped outside his home in Gulf Breeze, Fla. When he saw a person jump out of the bushes, he pulled the trigger.

Only then did Dennis realize who the person was: his son-in-law.

Christopher Bergan had flown 4,500 miles from Norway, where he and his wife live, to get to the Florida Panhandle. It was supposed to be a birthday surprise for Dennis, who was turning 62 the next day. Instead, it was a tragedy: The bullet hit Bergan "straight in the heart," Santa Rosa County Sheriff Bob Johnson said, killing the 37-year-old instantly.

Calling the shooting a "tragic accident," authorities announced on Thursday that they wouldn't be pursuing criminal charges against Dennis.

"I'll tell you this much: Anybody who's religious out there, you need to pray for this family because this is - I can't imagine what they're going through," Johnson said during a news conference. "I really can't. It's horrible."

In a coincidence that may have contributed to Dennis' state of mind the night of the shooting, another relative had pounded on his front door at about 9:30 p.m. The two had a "verbal altercation," Johnson said, and Dennis chased that relative off.

Bergan probably didn't know that when he landed at the airport around 11 p.m. and headed to Dennis' house. A Norwegian citizen, Bergan had lived in Florida for years before returning to his native country with his wife.

After Dennis realized whom he'd shot, the family quickly called 911. They pressed towels to his chest in a desperate attempt to stop the bleeding, authorities said. But it was too late.

Because of the earlier confrontation, the sheriff said, he wasn't going to "second-guess" Dennis.

"I mean, here he is, he just had a confrontation at the front of his house," Johnson said. "A couple hours later, someone else is banging on his backdoor. It's a fenced yard, somebody jumps out of his bushes - you can't really say anything against Mr. Dennis for doing what he did. I think it was just a horrible accident that should never have happened."

The family was devastated by what happened. In an interview with Oxygen.com, neighbor Patty Munzell described Dennis as "a kind man." He has "lost a best friend," she said.

"I think that it will take a long time for the family to heal," Munzell said, "if ever."