Geradot broke into the house, shot Chapman as soon as she walked in and then she shot herself, Colarulo said.
"There were emails and text messages indicating what she planned to do, and the detectives are still sorting that out," he said.
Officials believe Gerardot may have disguised herself and taken a train from Delaware, since a wig and other clothing not belonging to Chapman were found in a bag inside the house.
Chapman, a 2007 graduate of the University of Delaware, worked for the school in media relations and marketing and ran unsuccessfully for a state Senate seat in Delaware in 2016. She recently was hired as an assistant vice president at Villanova University.
Delaware Online reported that less than two hours before she was killed, Chapman said on her Instagram account that she "couldn't be more excited" about her new position.
"Just a week on the job and I'm already feeling the love from #NovaNation! #GoingNova #HigherEdMarketing#NewAdventures." she posted at 5:42 p.m.
Villanova University spokesman Jonathan Gust said the school was informed Monday night about her death.
"Our hearts are broken by the devastating loss of our new colleague," he said. "The thoughts and prayers of the entire university community are with her family, friends and colleagues during this extremely difficult time."