use a group by query - group by employee name and count the number of accidents.
Any employees that have not had an accident will not appear in the list. If you need zero accidents to be reported as well, create a new query with the employee table left joined to the group by query and use the name from the employee table.
something like
qry1:
SELECT empID, empname, count(*) as NoOfAccidents from tblAccidents group by empID, empname
qry2:
SELECT tblemployees.empname, NoOfAccidents
FROM tblemployees LEFT JOIN qry1 ON tbleemployees.empID=qry1.empID