My toy chihuahua was attacked today in my front yard by my neighbors two large aggressive dogs. Who is liable?

My dog is in icu. We don't know much. Will know more in 24 hrs. She's sedated and in an oxygen tent, iv, and on meds. Torn muscle in lung area. Estimate is between $1100 and $2600. Depend sit nothing else is wrong and if it heals on its own. Who is liable for the vet bills?