Sgt. Kenneth Reda was afraid his wife would find out he was having an affair.

He didn’t want anyone to know that his mistress, Shelley Powell, was out on his boat with he and his best friend, Brent Stephens, last April, and that they had all been drinking.

So when Stephens, a fellow Cobb County SWAT team member, went overboard on Lake Allatoona, Reda didn't call 911 for more than an hour, according to testimony Thursday in Cherokee County Superior Court.

He took Powell, his co-defendant, to shore and then began telling a series of lies to authorities.

“You saved yourself instead of saving your friend,” said Judge Frank Mills.

Reda was sentenced Thursday to four years in prison and nine years probation in Stephens drowning death and the cover-up afterward. Reda admitted lying to authorities the night of the accident and into the next day as they searched for his friend.

Reda said he was sorry Thursday.

“Brent was my best friend,” said Reda, taking lengthy pauses between sentences to keep his composure. “If Ms. Powell hadn’t been on that boat, if I hadn’t been trying to hide a relationship with her, this wouldn’t be where it is now.”

Reda, who lived in the same Acworth neighborhood with Powell and her husband, pleaded guilty earlier this month to second-degree homicide by vessel, tampering with evidence, three counts of making false statements and violation of office by a public officer.

As he was led away in handcuffs Thursday, Reda mouthed to his teary wife, Missy, “Be strong. Be strong.”

Missy Reda, who eventually found out about the affair, decided to stay with her husband. She said she understands why her husband originally lied to authorities.

"He was having an affair, and doing his best not to get caught," she said.

Authorities believe Reda’s boat struck a pylon April 22, as he, Stephens and Powell were returning home from dinner. Stephens fell overboard and drowned. According to the autopsy report, Stephens' head was hit by a blunt object, possibly part of the pylon.

After Reda, 38, and Powell could only find Stephens' flip flops floating in the dark water that night, Reda dropped Powell off at Harbor Town Marina in Acworth, giving her a trash bag of beer, plus a cooler from the boat.

Reda then returned to the lake. About 90 minutes after Stephens, a father of two, went into the water, Reda made his first 911 call.

He said he’d been alone with Stephens, a former Army Ranger, on the boat. He said his friend might have jumped overboard and could be on shore already.

An agonizing night began for the friends and loved ones of Brent Stephens.

“Ken knew he wasn’t on shore,” said Sheila Stephens, Brent’s mother. “He let us have hope, when he knew there was none.”

Stephens’ body was found the next afternoon in the water.

His widow, Lori, testified Thursday that their children don’t understand what happened to their father.

She said their 4-year-old son asked how far away heaven was, and could they take a rocket ship to visit him.

Amid the emotional testimony that even had Judge Mills choked up, Lori Stephens talked about the hole in her life now that her high school sweetheart is gone.

“I always come home to an empty house,” she said softly. I lost my husband, “not in the line of duty but in the hands of a friend.”