do you think den hollander was jealous of marc? absolutely.revenge. most assuredly, yes. andrea canning (voiceover): the pieces of the puzzle were now coming together quickly. the fbi determined the gun den hollander used to kill himself was the same one he used to kill daniel and marc angelucci. same 380 caliber handgun, which was legally purchased in the 1980s. andrea canning (voiceover): agent denahan and his team tracked den hollander's movements minute by minute. his two-week spree began when he got on a train in new york city. and he took amtrak out to california, bringing the weapon with him. andrea canning (voiceover): surveillance cameras captured him at the los angeles train station and at the one in san bernardino. he spent a few days in the area, denahan says, most likely tracking marc, waiting for the perfect time to kill him. and then how does he get back? same way. he immediately returned the same way. andrea canning (voiceover): he then picked up the silver rental car in philly and drove to new jersey. tracking his cell phone,