Police have sealed off the area around the New England Pentecostal Church, citing an "active investigation".
CNN reported that two people were transported to a hospital with gunshot wounds, but their conditions were not known. A third person suffered minor injuries while subduing the male suspect.
It's unknown if the two people shot were part of the wedding or there as guests.
"This does not seem to be a random event, at least at this point", Roark said during a news conference Saturday afternoon outside the police department.
Halloway taken into custody after some of the approximately 40 guests at the wedding "gang tackled" him and held him down until police arrived, Roark said.
The town of Pelham is located in southern New Hampshire, 23 miles south of Manchester.
The service was for Luis Garcia, 60, a minister at the New England Pentecostal Ministries for six years, who was shot and killed October 1, according to WMUR.
A spokeswoman for Lowell General Hospital in MA said they are treating one victim from the shooting, but did not release any additional information. According to his obituary, he was a minister at the church.
Roark said the New Hampshire attorney general's office would provide more details later Saturday. Brandon Castiglione, 24, has been arrested in relation to the crime.
New Hampshire Governor Chris Sununu said that state officials are on scene assisting local first responders with the incident.