How to start an animation of some object while destroying other object?

I want to start the animation when destroying another game object. How is this possible? To have this in mind I was trying to use setActive() in the else statement where the object is destroyed. However, nothing happens, only it does activate when I put it inside if(target). So I'm trying something like this:

public void Update()
    {
        anim = GetComponent<Animator>();
        anim.SetBool("isWalking", isWalking);
        if (target)
        {
            
            bar.fillAmount = (float)health / baseHealth;

            float distance = Vector3.Distance(transform.position, target.transform.position);

            if (distance >= attackRange && isAttacking)
            {
                isWalking = true;
                agent.SetDestination(target.transform.position);
            }
            if (distance - 1 <= attackRange)
            {
                isWalking = false;
                agent.ResetPath();
            }
            if (distance - 1.5 <= attackRange && Random.value < Time.deltaTime && Time.time > lastAttackedAt + cooldown && agent.remainingDistance <= agent.stoppingDistance)
            {
                isAttacking = true;
                isWalking = false;
                Attack();
                lastAttackedAt = Time.time;
                anim.SetTrigger("isAttacking");
            }

        }
        else
        {
            OnDeath();
            spawnPortal.SetActive(true);
        }
    }

The object is well destroyed but still the animation does not appear. It remains hidden (unchecked)...