Even without Google or Apple, they police have the cell service providers. In the case of the Austin bomber from a year ago[0], police got cell tower records from the multiple bombings and figured out who was at all the locations. Cell phones are little trackers unless you turn them off or don't carry one. [0] https://www.google.com/amp/s/www.nbcnews.com/news/amp/ncna85...
>"But despite the drawbacks, detectives noted how precise the data was and how it was collected even when people weren’t making calls or using apps — both improvements over tracking that relies on cell towers."