His assistant, a woman in her 60s who associates identified as Judy Elliott, was taken to a Fort Worth hospital. A close friend said she sustained a heart attack and is in intensive care.
Police said a friend of the one of the victims called 911 shortly after 4 p.m. after spotting them inside the church.
"That person came to the church, was walking around the building, looked into one of the windows and spotted someone on the ground not moving, and so they called 911," police spokeswoman Tiara Ellis Richard said.
Investigators say robbery could be a motive, but they are not ruling anything out in the case.
The assistant's car, a cream-colored, four-door Mitsubishi Galant with Texas license plate DFR 352 is missing.
Police said anyone seeing the car should call 911 and not approach the vehicle.
NorthPointe Baptist Church is a satellite campus of First Baptist Church of Arlington.
Dobson graduated from Baylor University in 2004 and also later earned a master's degree in divinity from the university. He received an Outstanding Student Preacher Award at Baylor in 2008.
"What's lost is a good friend, a person everyone felt close to (and) loved, a young man that was just building his career as a minister," church member Tillie Burgin said. "He was loved by many, many people."
The church's website said Dobson loved "reading, watching football, being a fanatic for the Texas Rangers, drinking coffee and spending time with my amazing wife."
Burgin described him as a "sweet, gentle, great guy."
"This church will continue because of his leadership," she said.
NBC DFW's Ellen Goldberg contributed to this report.