update integer array elements atomically C++

Given a shared array of integer counters, I am interested to know if a thread can atomically fetch and add an array element without locking the entire array?

Here's an illustration of working model that uses mutex to lock access to the entire array.

// thread-shared class members
std::mutex count_array_mutex_;
std::vector<int> counter_array_( 100ish );

// Thread critical section
int counter_index = ... // unpredictable index
int target_face_particle_count;
{
  std::lock_guard<std::mutex> lock(count_array_mutex_);
  current_count = counter_array_[counter_index] ++;
}
// ... do stuff using target_face_particle_count.

I'd like multiple threads to be able to fetch-add separate array elements simultaneously.

So far, in my research of std::atomic<int> I'm thrown off that constructing the atomic object also constructs the protected member. (And plenty of answers explaining why you can't make a std::vector<std::atomic<int> > )