. >> investigators immediately took bruno santos in for questioning. >> i could describe him as a veryocky, arrogant, young man, somewhat confrontational at times, pretty hard to deal with. he told me that he had proposed to sarah or asked her to marry him, which she said yes. >> bruno and his mother claimed bruno was home asleep on the morning of the murders, but no one else could verify his alibi. >> he was cooperative with us at the time. as we started pushing him a little harder in interviews, his demeanor certainly did change. >> my first thought was bruno. we figured he was angry with diane and alan, he decided to get rid of them so that he and sarah could be together. >> investigators also found evidence that santos defied the johnsons and continued to see sarah, going so far as to have sexual relations with her in her own home. >> we confirmed that by finding semen stains on sarah's sheets that matched bruno, so we knew that he had been in the house. so, he was a prime suspect based on the fact that this crime truly was committed by someone with knowledge, access and opportunit