HOUSTON -- A birthday celebration ended in tragedy after an armed man stormed into a Houston-area and opened fire. 

Harris County Sheriff's investigators said Myrtle Smith was shot to death by her estranged husband, Charles Smith.

At least 20 people were inside the home at the time of the shooting. They were celebrating the birthday of the couple's 41-year-old daughter.

The victim’s nephew, Don Terrell, was the first to encounter his uncle at the door.

"I was going to go home. I was holding open the door and he was sitting right there with the shotgun," he said.

Terrell said he slammed the door shut and yelled out a warning.  Then he ran to a rear window to escape.

Once outside, he called 911.

Harris County deputies arrived within five minutes.  When they got to the scene, they found the suspect inside the house with a gun pointed at his head.

"He was saying such things as, I shot my wife. I know I am going to get the electric chair," said Lt. John Legg of the Harris County Sheriff’s Department.

Legg said Smith lowered his gun, but then raised it again.

Smith shot himself in the head at the same time a deputy shot him in the right leg.

"According to both deputies at the scene, the gun shots were heard almost simultaneously," said Legg.

Investigators said they found a total of three weapons and extra rounds on Smith.

"If I hadn't called 911, he would have killed a whole lot of people," said Terrell.