When Orange and Anaheim shut down the 700 person homeless camp that had erupted along the Santa Ana River Trail they found that the homeless were roughly 1/3 drug and alcohol abusers, 1/3 mentally ill, and 1/3 criminals. With the three groups blending in many cases.
There weren’t any illegal aliens, probably because they have long been used to living 20 to a house to share the rent. Our local cities turn a blind eye to the overcrowding and let neighborhoods go to hell.
If that was the official summary, it's a fair bet ~90% were druggies.