Justin Poore said he saw Campbell twice the night of Heather Domenie's murder. Poore told jurors he came by to show off his new car and the door to Campbell and Domenie's home was open.
"I stuck my head in and yelled, 'Hey guys, it's me. I'm here,'" he said.
Prosecutors are trying to piece together the series of events leading to Domenie's death. Campbell admitted responsibility for Domenie's death, but he claims he did not mean to do it.
Poore testified Campbell told him Heather was ill then rode around the block with him in his new car, but Poore said Campbell was not himself.
"He was solemn," Poore said.
Later that night, Campbell called Poore and told him Heather was hurt. Poore came over and saw emergency vehicles and Campbell crying.
"He was really shaking badly and hyperventilating. A couple of times, I felt he was getting ready to black out," Poore said.
The next day at lunch, Poore said Campbell ate a big plate of food and complained about being unable to collect on an insurance policy he and Campbell applied for.
Prosecutors claim Campbell wanted Domenie dead so he could collect the money and go to the Bahamas with another woman. Prosecutors say they plan to rest their case against Campbell on Monday.