Why? The article plainly says the officer sent the text to him and gave him McMichael's contact info after McM volunteered to check on the house for him. If they already knew each other, or had any contact, McM could have just told English himself, or been put on the alarm list or whatever. Based on available info, McMichael inserted himself into the whole situation by volunteering to check things out if English would alert him.
I can literally hear that conversation between McM and the cop. McM shows up when he sees the cop, IDs himself as one of them and asks what's going on. "Oh hell, man, y'all have enough to deal with without a bunch of bogus alarms so just give the owner my info and I'll run down here and check it out for you and call if there's anything to it." And Barney does as he suggests because he's a lazy piece of shit with stars in his eyes.
Cowboy up, motherfucker. Hope it was worth it to you.