My phone recently buzzed with an alarming notification: Police officers were responding to a shooting about a mile away.

A few hours later, another alert popped up, letting me know that two men were fighting in an alleyway nearby. Then my inbox loaded an email with a message that a neighbor had found a man trying to break into his house.

The notifications arrived because of two apps I was using: Nextdoor, a social network for neighbors , and Citizen, which delivers alerts on local crimes in progress. Both are among the most downloaded news apps today, according to App Annie, the research firm.

They are also part of a crop of apps that focus on keeping people informed about their neighborhoods, a category that is likely to grow. Last year, for instance, Amazon acquired Ring, which makes a doorbell that doubles as a security camera. The retail giant recently posted a job listing for someone to manage a team of news journalists who would write crime alerts for an app.