My niece had problems in her home before covid. She thinks her kids friends might have brought them in but who knows. But I feel for you just knowing what she went through. I know she used this product (EcoVenger Bed Bug Killer) and had great success. It took several treatments (used full strength in a spray bottle), but she managed to rid them completely. I know she sprayed everything and every nook and cranny and it worked. A bonus is that it is also non toxic. It is made from a natural oil called neem. I know she bought hers from Amazon, but other retailers might also sell it. Good luck!!
https://www.amazon.com/gp/product/B00FTWO27G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
First thing to do is seal up any cracks or crevices where the bugs can enter the apartment. Also use a clear caulk on the baseboards if there are any exposed spaces, no matter how tiny.
Get all beds and furniture steam cleaned (if possible) and treated. Use mattress covers. Get the carpet steam cleaned, too. This kills the live bugs.
Buy this: https://www.amazon.com/EcoRaider-Killer-Non-toxic-Extended-Protection/dp/B00FTWO27G. It's expensive, but it works. Depending on the size of the apartment, you'll need at least three, possibly more. It works by killing both bugs and eggs, and disrupting the breeding cycle.
Vacuum the entire apartment, spray everywhere, even inside drawers and closets. Move all furniture away from walls and spray, spray, spray.
Wash all clothes, sheets, blankets, anything that's been exposed, in hot water and dry on high heat for at least 30 minutes. You will need to do this weekly for a couple of months.
Repeat steps as necessary. (Except the beds; they only need to be done once. The covers will keep the bugs from reinfesting the mattresses. Make sure to change and wash bedding often, though, so they don't bite your dad or anyone else.
Use diatomaceous earth along baseboards, behind furniture and under beds. If you vacuum a lot (and you may have to), remember to put more down.
Clean out the vacuum thoroughly every time you use it. If it has a dust cup, wash it and clean the filters. Empty dust cup contents into a bag separate from the rest of the trash, tie it off and take it out immediately. When you're done with treatment, retire the vacuum.
Did this exact thing in a studio apartment. The bugs were complately gone after six weeks and never came back. Hope it works for you.