How long is "shortly?" Long enough for them to kill Mr. Horn? But in any event, considering they hadn't arrived in those 7 minutes, and that Mr. Horn could not know that the police were going to come along "shortly".
BTW, while they were thieves, what's important under the law is that they were also burglars.
Maybe long enough for them to kill everyone in pasadena, galena park, la porte, clear lake, seabrook, and deer park. Good thing Mr. Horn shot them when he did.