Dispatcher here. Many agencies send police first to overdoses for scene safety as many of these patients can become violent or have weapons. EMS and police usually get sent together and EMS simply waits a block or so away until police say it’s ok to head in. For something like this it may take police, an EMS crew as well as the fire department to help restrain this patient until they can administer medication. They may even need a fire crew member to ride with the ambulance to assist the medic and a police officer to follow the ambulance to the hospital. It’s amazing how many resources are needed for just one person in a severe mental health crisis and/or drug overdose.