What are these very little tiny black bugs on my bed?!

What are these very little tiny black bugs on my bed?

its actually in my baby's room..she sleeps in the crib tho but this bed is in her room as well..i had just taken out the bed sheet from it like a week bak..n today wen i was changing my baby..i found these lil tiny black bugs..they'r not even tht noticeable..thts how tiny they are..i just saw them moving here n there..i killed the ones tht i found rite there by smacking them..but i need to kno wat they are and how do i get rid of them from my mattress??
cuz im afraid watever these r..there may be more..n probly some laid eggs too!! the mattress is not even old at all..i bot it last yr in may...plz help!! thanku :)

1 month ago
ok again my daughter's crib is in tht room and also another bed..the bugs tht i found are not in my babies crib..i found these bugs on the other bed's mattress

THOSE ARE LIKE CRABS OR BEDBUGS! GIT RID OF EM QUICK!