Witnesses said the gunman was dressed in black, wore combat boots and carried an automatic assault rifle.
Jesse Gingrich was in her car in the church parking lot Sunday morning when she saw the gunman open fire.
"The man pulled out a huge rifle and my first thought was, that can't be a real gun," Gingrich told "Good Morning America." "It was so surreal to me at the time."
Gingrich said the gunman was right next to her car and began shooting at a van in a spot diagonal to hers.
"I ducked down in my car. … I couldn't find my car keys," Gingrich said. "I was absolutely positive I was going to be next."
New Life is one of the largest churches in the country and no stranger to controversy. The church's founder, Ted Haggard, was fired last year after a male prostitute accused him of paying for sex and crystal meth.
Haggard and the New Life Church had links to Youth With a Mission. The two groups worked together on a controversial missionary program that focused on converting people in Muslim countries to Christianity.
About 7,000 people were on the church campus at the time of the shooting, said Boyd.
"What happened today was a real tragedy and as a pastor, my heart is broken today for people that lost their lives," Boyd said.
The Associated Press contributed to this report.